In the regeneration of a DPF for removing PM accumulated on the DPF by burning the PM using heat of an exhaust gas, there is a conventional exhaust treatment device for a diesel engine in which the temperature of the exhaust gas on the upstream side of the DPF is raised by increasing the target rotation number of the engine so that the main injection of fuel is increased (refer to FIG. 9 of Patent Document 1).
According to this kind of the device, there is an advantage in that the regeneration of the DPF can be accelerated by a rise in the temperature of the exhaust gas.
In this conventional technology, however, a problem arises because the target rotation number of the engine is suddenly raised all at once.    [Patent Document 1] Japanese Patent Publication No. 2005-113752